The 24-hour Pollutant Standards Index (PSI) on Monday (Sep 14), the first day of school after the term break, is expected to be in the mid to high sections of the Unhealthy range.The National Environment Agency (NEA) first gave this update just after 6pm on Sunday, when the 24-hour PSI was 126 to 146, the low to mid sections of the Unhealthy range. It also added that the the 3-hour reading may tip into the Very Unhealthy range - above 200 - if unfavourable winds bring in denser haze from Sumatra.The 3-hour PSI later peaked at 222 at 1am before dipping to 65 at 8am on Monday, while the 24-hour PSI remained in the Unhealthy range at 131-156. However, the air quality began worsening again, with the 3-hour PSI rising to 86 at 12pm, while the 24-hour PSI at the same time was 121-145.Thundery showers forecast in the late morning and early afternoon on Monday may bring only a "short, temporary respite", noted the NEA.The current haze is the worst in two years, and several public events scheduled Sunday were cancelled. The Singtel-Singapore Cancer Society Race Against Cancer was called off the night before “for the safety and health of runners, volunteers, staff and beneficiaries”, said organisers. The POSB PAssion Run For Kids had its 10km Adults’ Competitive race and Kids’ Run categories pulled from the line-up at 5am, when the 3-hour PSI was 147.However, as the focus shifts to pupils heading back for classes, schools and parents seem prepared, with precautionary measures ready.The Ministry of Education (MOE) and schools have a continuity plan in place to ensure the well-being of students and staff during a haze situation. For example, teachers will be on the lookout for students who are unwell and ensure that they receive prompt medical attention.“Schools are ready to respond and take appropriate haze management measures based on a set of guidelines corresponding to the health advisory,” the MOE said on its website. Some principals told TODAY their schools have masks and air purifiers, which would be used when the need arises.Ang Mo Kio Secondary principal Abdul Mannan said his school has more than 10 air purifiers and a list of students with respiratory problems. The school will install them in those students’ classrooms if the PSI reaches the very unhealthy level.He added that the school will use the 24-hour PSI range to decide on its contingency plans. “If it (remains) consistently high, then we’ll do something about it. That’s why we always use the 24-hour number as a more accurate gauge,” said Mr Abdul.Punggol View Primary principal Kelvin Tay said that when the PSI is in the unhealthy range, the school reduces strenuous activities and moves Physical Education lessons indoors. His school will issue a letter on Monday to inform parents about their plans to deal with the haze situation.Mr Tay added that parents should also be mindful of their children’s condition. “It’s important that the children are hydrated and to encourage them, if they feel uncomfortable, to wear a mask,” he said.Parents TODAY spoke to have been equally prepared for the worsening haze situation and are hoping schools act accordingly.Mr Adrian Koo, whose son is in Primary Four, was worried that the haze might cause health issues for students. “For the entire school holiday period, we have kept him indoors,” said the 38-year-old. “Schools should stop all PE lessons or sport activities until the haze situation improves.”Human resource practitioner Shirley Tan, however, is not “too jumpy” about the haze situation, compared to the record high three-hour PSI of 401 in June 2013. Still, the 42-year-old, who has two children aged nine and 11, has masks at home for her children to wear “if they are having respiratory problems” or if the PSI level reaches “close to 200”.